Chapter 84 covers nuclear reactors, boilers, machinery, mechanical appliances and their parts, and is one of the broadest chapters in the HS. This chapter includes power machinery, pumps, fans, refrigeration equipment, machine tools, office equipment, automatic data processing equipment, transmission devices, etc. Its core feature is that goods must have a mechanical function or serve as dedicated parts of machinery, rather than merely being materials or simple articles. The chapter notes clarify the rules for priority classification and the principles for classifying parts, and provide guidance for the classification of engines and their parts. Heading 8409 is dedicated to "parts suitable for use solely or principally with the engines of heading 8407 or 8408." Heading 8407 covers spark-ignition reciprocating or rotary internal combustion engines (such as gasoline engines), and heading 8408 covers compression-ignition internal combustion engines (such as diesel engines). Therefore, 8409 covers parts dedicated to gasoline engines and diesel engines, such as pistons, connecting rods, cylinder blocks, cylinder heads, valves, carburetors, fuel injectors, etc. However, it should be noted that certain parts, if also usable with other machinery, may not be classified under this heading. Code 840991 is a six-digit subheading: the first 2 digits "84" represent Chapter 84 (machinery); digits 3-4 "09" represent heading 8409 (engine parts); digits 5-6 "91" represent subheading 840991, namely "parts suitable for use solely or principally with spark-ignition internal combustion engines." Therefore, 840991 specifically refers to parts dedicated to gasoline engines (spark-ignition), while 840999 is used for parts dedicated to diesel engines (compression-ignition). This subheading is a six-digit HS code, and countries may further subdivide it into eight-digit or ten-digit national codes. The goods are gasoline engine parts. Gasoline engines belong to spark-ignition internal combustion engines and are classified under 8407. Their dedicated parts should be classified under 8409, and the subheading should be selected according to the engine type: spark-ignition under 840991, and compression-ignition under 840999. Therefore, 840991 is the correct classification. If the parts are general mechanical parts (such as bolts, gaskets), they may be classified under other headings (such as 7318, 8484, etc.) rather than 840991.

Product name: The Chinese and English names of the declared part should be specific and clear, such as "gasoline engine piston," "gasoline engine carburetor," etc., and vague wording such as "engine parts" should be avoided. Use: Explain what kind of gasoline engine the part is dedicated to or principally used with, such as "used for automobile gasoline engines," "used for motorcycle gasoline engines," etc. Material: Declare the main material of the part, such as aluminum alloy, cast iron, steel, plastic, etc., which affects classification and customs valuation. Brand: Fill in the manufacturer or brand name; if there is no brand, indicate "no brand." Model: Fill in the model or part number of the part to facilitate identification of the specific part. Applicable engine type: Clearly state whether it is spark-ignition (gasoline engine) or compression-ignition (diesel engine). This is the key to classification under 840991. Whether it is a general-purpose part: Explain whether the part is dedicated to gasoline engines or can be used generally with other machinery. Example of customs declaration form declaration: Product name: Gasoline engine piston Use: Used for automobile gasoline engines Material: Aluminum alloy Brand: XX Model: ABC123 Applicable engine type: Spark-ignition Whether it is a general-purpose part: Dedicated Specification: Diameter 80 mm Remarks: This part is dedicated to a 1.6L displacement gasoline engine and is not a general-purpose part. Confusing gasoline engine parts with diesel engine parts, and mistakenly classifying diesel engine parts under 840991. Incorrectly classifying general-purpose parts (such as bolts, gaskets) under 840991, when they should actually be classified according to material. Failure to provide the applicable engine type, leading customs to question the classification.

The core basis for classification is General Rules of Interpretation 1 and 6 of the HS, the chapter notes to Chapter 84, and the text of heading 8409. First, determine whether the goods are engine parts and whether they are dedicated to or principally used with spark-ignition internal combustion engines (gasoline engines). If they are parts dedicated to gasoline engines, classify them under 840991; if dedicated to diesel engines, classify them under 840999; if they are general-purpose parts, classify them according to material or function. At the same time, reference should be made to the detailed explanations of 8409 in the Explanatory Notes to the Harmonized System. 840999 Diesel engine parts: 840999 is dedicated to parts of compression-ignition internal combustion engines (diesel engines), while 840991 is dedicated to spark-ignition engines (gasoline engines). The key distinction lies in the ignition method of the engine. 8407 Spark-ignition internal combustion engines: 8407 is the complete engine, and 840991 is its dedicated parts. If a complete engine is imported, it should be classified under 8407; if it is a part, it should be classified under 840991. 8483 Transmission shafts, bearings and other mechanical transmission parts: 8483 covers general transmission parts, such as crankshafts, camshafts, etc., but if they are dedicated to gasoline engines, they should still be classified under 840991. If they are general-purpose parts, they are classified under 8483. 8413 Pumps: Fuel pumps, water pumps, etc. used for gasoline engines, if dedicated to engines, should be classified under 840991; if they are independent pumps, they are classified under 8413. 8484 Gaskets or similar joints of metal sheeting: Gaskets used for engines, if dedicated, are classified under 840991; if they are general-purpose gaskets, they are classified under 8484. Are the parts dedicated to gasoline engines? Can they be classified under other headings (such as general-purpose parts)? Has proof of engine type been provided? Has the complete engine been confused with the parts? Have the tariff notes been consulted?

How can one determine whether a part is dedicated to a gasoline engine or a diesel engine? Mainly by looking at the design and working principle of the part. Gasoline engines use spark plug ignition, while diesel engines use compression ignition. For example, carburetors, spark plugs, distributors, etc. are usually dedicated to gasoline engines; injection pumps, injectors, etc. are dedicated to diesel engines. If the part drawing or manual indicates the applicable model, this can be used as a basis for judgment. Under which code should piston rings for gasoline engines be classified? Piston rings for gasoline engines are dedicated parts and should be classified under 840991. However, note that if the piston rings are general-purpose parts, they may be classified according to material. It is recommended to provide proof of the applicable model when declaring. If a part can be used for both gasoline engines and diesel engines, how should it be classified? If a part is suitable for both gasoline engines and diesel engines and has no principal use, it cannot be classified under 840991 or 840999, and should be classified under other headings according to its material or function. For example, general bearings are classified under 8482. When importing gasoline engine parts, what declaration elements must be filled in on the customs declaration form? Product name, use, material, brand, model, applicable engine type, etc. must be filled in. Specific elements may refer to announcements of the General Administration of Customs. It is recommended to provide detailed technical materials to avoid classification disputes. Are the tariff rates for 840991 and 840999 the same? The rates may differ and may be adjusted with national policies. Specific rates should be checked in the latest Import and Export Tariff or customs system. The actual determination by customs should prevail; this answer does not provide specific rates. Under which code should the ECU (electronic control unit) of a gasoline engine be classified? If the ECU is dedicated to the engine, it is usually classified under 840991; but if it is a general-purpose control module, it may be classified under 8537 or 8543. Judgment should be based on its function and specificity. How can one inquire about the national subheadings under 840991? You may consult the China Customs Import and Export Tariff or log on to the website of the General Administration of Customs. National subheadings are usually 8-digit or 10-digit, such as 84099110, etc., and are further subdivided according to part type. What special documents are required for import when parts are classified under 840991? Generally, basic documents such as contract, invoice, packing list, and bill of lading are required. If brand authorization is involved, an authorization letter is required. In addition, it is recommended to provide part drawings or manuals to prove specificity.